Which Mac is suitable for Blender 2.8?
The most important component for Blender is a good graphics card. Unfortunately, to get an even remotely decent GPU (Graphics Prcessing Unit) on a new Mac you'll be looking at $3K+, certainly not worth the money.
Macs these days come equipped with AMD cards which have sup-par support for GPU rendering. Even if you could somehow get an NVIDia card to work on your Mackintosh, Apple decided to deprecate third party toolkits on their platform, thus making CUDA unavailablke for GPU acceleration of Cycles renders.
Additionally, given that also Apple decided to deprecate support for third party graphics APIs like OpenCL and OpenGL in favor of their own Metal API you will always be looking at a feature crippled system when compared to competing platforms in terms of GPU rendering and real time drawing performance, which makes MacOS an even less of an advisable ecosystem to invest in if you are seriously looking at open source software.
For that reason, I cannot recommend a Mac for Blender.
With a gaming PC, you could buy something with very good specs for about \$1~1.5K. A laptop with specifications like Intel Core i5 for CPU and 8GB RAM would also work just fine, and you can find a laptop with an NVIDIA GTX 970 on Ebay/Craigslist for pretty cheap these days.
For the NVIDIA 10 GPU series cards a GTX 1060 would be a good entry point. NVIDIA will soon release new GPUs for their 20 series. Laptop with a 20-series GPU might be a bit expensive though, but it might be worth-it specially if you were planning to spend ~$3k for a MacBook Pro.
If you absolutely have to buy a Mac then the 15&quot; MacBook Pro is probably the best bet. It's the only laptop in Apple's lineup with a dedicated GPU, the MacBook Air/12&quot;/13&quot; all use integrated graphics which is admittedly insufficient for Blender 2.8 (it's too slow).
Related

What are the limitations of Blender for Mac?
eGPU + Blender + Cycles + Mac
eGPU Vega 56 (Blackmagic) Mac + cycles problem